Joel. I'm a bit confused
First the easy bit, the inner polyline is not closed, whereas the outer one is closed, see attached for pic of where it is not closed. One could just go into edit tool mode, hover over a node, right click and click close, BUT this will add a small unwanted line where the two nodes don't quite meet. (zoom right in on the location in the pic to see they are open).
What I would suggest is, In edit tool mode, zoom right in so you can select the node at the end of the long straight line. select it (drag a small selection window around it so the node turns red). right click and choose 'delete node'. hover over any other node, right click and choose 'close'
This will produce a properly closed without adding an unwanted kink. However. being totally honest. I'd personally redraw the whole thing using polyline / arcs. to get a smoother object than lots of small segments (but that is just me).
What I am confused about is the 2d add. why. It looks like the middle should be a hole, in which case 2d subtract would be required. However 2d subtract will produce a region object, which cannot be extruded, one can go into the regions properties and 3D, choose solid, and give it a thickness. There are plenty of alternatives depending on whether it is being just 2D or made into 3D.